Significant strides have been made in our understanding of the initial events of sensory transduction in taste cells during the last two decades, yet little is known about the mechanisms of intercellular com- munication within the taste bud. Only one-fifth of the taste cells in a mouse taste bud havemorphologi- cally identifiable "classical" synapses from the taste cell onto an afferent nerve fiber. Little, however, is known about the molecular features of neurotransmitter release at these sites in taste cells. It is significant that not all taste cells thought to play a role in sensory transduction have classical synapses. Taste cells that display gustducin immunoreactivity respond to bitter compounds, yet our preliminary data suggest that they do not have classical synapses onto nerve processes. Howthen does information pass from these bitter-sensing cells to the central nervous system?We have observed taste cells in the mouse that have unusual contacts with nerve processes in which subsurface cisternae (SSC) of smooth endoplasmic reticulum or large, atypical mitochondria with tubular cristae are located only at the close appositions with nerve processes. This proposal explores the possibility that these zones of close apposition may serve as nonclassical synapses, i.e., zones where information is trans- mitted from taste cells to nerve fibers via mechanisms other than the classical synapses. The goalof this grant application is to test the hypothesis that both classical synapses andnonclas- sical taste cell-nerve fiber contacts are important in transmission of gustatory information from taste cell to nerve fiber. During the next funding period we will utilize immunocytochemistry, in situ hybridization and electron microscopy to investigate both classical and novel contacts between taste cells and nerve fibers to accomplish the following aims: Specific Aim 1. What molecular machinery is present at morphologically "classical" synapses? Specific Aim 2, What is the nature of nontraditional taste cell-nerve fiber contacts?